You know the drill. The Difference is a reflection on the game that was, with one bullet for every point in the final margin.

If you focus on three of this game’s four quarters, what appears is another close loss to a good team.

But if you stumble across the dreaded third quarter, the worst of quarters known to man or woman (other than the 2003 Not-Centennial Quarter of A Quarter), things become impossibly bleak.

The Rockets outscored the Mavericks 44-17 over the course of a 12-minute period. Yes, the Mavericks allowed 44 points.

That 44-point mark is the most the Mavericks have allowed in a single quarter this season, and hopefully that record will hold for the remaining 23 games.

As faulty as single-game plus-minus is in the realm of statistics, the fact that every Houston starter had a +26 or better speaks volumes about the way Dallas began a tumultuous second-half.

Speaking of +/- and other symbols, tonight held a certain sadness beyond the final score.

The sterling career of consummate professional Shawn Marion experienced a slight tarnish, as he posted the worst plus-minus of his career, at -35.

So what went wrong? Such a wide-ranging question is difficult to quantify with a simple answer, but it begins with perimeter defense, a prevalent issue for the Mavericks all season, and never more so than tonight.

Chandler Parsons (12-13 FG, 6-7 3PT, 32 points) isn’t the greatest jump-shooter to grace this storied Earth, but he is enough of a well-rounded player to seize countless open opportunities.

Such opportunities came in spades tonight, especially from the aforementioned perimeter, as he made open looks that the Mavericks were so confusingly willing to allow him, especially in the late second and third quarters.

When you allow an opposing NBA team to take 34 three-pointers, you are almost assured to lose.

When the team in question is the three-point shooting-oriented Rockets, things are even more likely to go badly.

In the third quarter, a quick glance at the shot chart and a review of the game tape reveals a simple truth.

That truth is this: Over the course of those fateful minutes, the Rockets took an almost impossible number of three-pointers and lay-ups.

Those two types of shots, while broadly described, are definitively the most efficient shot types in the game of basketball.

A team that manages to primarily attempt those shot types will likely win, and the Rockets are such a team.

Esteemed GM Daryl Morey has often alluded to as much, and I’d guess he’s quite happy with how well the team’s methodology surged into the limelight as the game proceeded.

That methodology led to the following results in the 44-point third quarter, by my count:

A defense that allows an opponent to generate those levels of shot discrepancies will always fail, and so the Mavericks did.

It was apparent with every passing play that the Mavericks could not find a cohesive defensive strategy: either they overcommitted to the perimeter or allowed far too much room for Jeremy Lin (8-14 FG, 21 points, nine assists), James Harden (5-10 FG, 4-8 3PT, 21 points, seven assists), and Parsons to operate, despite all three being known dangerous quantities from beyond the arc.

Harden, in particular, was allowed far too much room to pull-up or spot-up throughout the game.

An example that comes to mind is in the middle of the third quarter. Harden is given too much room off an Omer Asik (4-6 FG, 10 points, 10 rebounds) screen, he penetrates into the lane easily, and then dishes to an open Parsons.

Vince Carter (4-8 FG, 2-5 3PT, 12 points, four rebounds) goes to close on Parsons, but his contest is hardly one at all.

It’s a half-hearted hand wave in the general direction of Parsons, but not a movement that would affect a solid, tall three-point shooter.

Now, the fault of a play like this, and the countless similar plays that followed and preceded it in this game, is not solely on Carter or any particular player.

It’s a systematic breakdown, apart from any single Maverick, coupled with mediocre individual defense on the part of Marion (atypical), Carter, and Brandan Wright (5-8 FG, 12 points, three rebounds), who didn’t step up to affect Harden in a significant way.

Such an occasion is symptomatic of the night, and fairly representative of the Mavericks’ defense over the course of this wayward season.

I’d like to finish this (hopefully) comprehensive missive by briefly discussing a single offensive facet.

By facet, I’m referencing the tepid play of Dirk Nowitzki (2-8 FG, 8 points, four assists, four rebounds) in tonight’s game.

After such a strong stretch of production over the last five contests, Dirk struggled mightily tonight.

My issue is not with the shots Dirk took (it rarely is), but with the lack of focus around him offensively, both due to his choices and the team’s various distributors. The Mavericks aren’t going to win many games when Dirk takes only eight shots over the course of 27 minutes, especially if none of those looks are three-pointers and few of them fall into the categories of “easy” or “within the flow of the game”.

They certainly didn’t win this one, and time is swiftly escaping the sporadic squad’s grasp with only 23 games and a fading dream left to hold.